BAGHDAD (Reuters) -- A bomb attack in Salahuddin Province damaged the Iraq-Turkey oil pipeline more than four days ago and the damage will take up to four more days to fix, an Iraqi Oil Ministry official said today.

The bombing was the second in less than a month, signaling a possible rise in attacks by insurgents or other groups on Iraq's oil infrastructure as it signs its first multibillion-dollar oil field deals with international firms.

The Kirkuk pipeline carries around a quarter of Iraq's oil exports to the Turkish port of Ceyhan, where it is pumped into tankers.

The Oil Ministry official, asking not to be identified, said a memo from the North Oil Company received by the ministry on November 23 stated the attack had occurred between the village of Shirqat -- a former hotbed of support for Al-Qaeda -- and Baiji oil refinery. The memo was marked "secret and urgent."

"Four days ago a sabotage bomb attack caused damage to the strategic pipeline near Shirqat," the memo read.

"Works are continuing to repair the damage. It's hard to determine when the flow will resume. It is expected the repair work will be finished in three to five days."

A shipping source in London said the flow of oil stopped on November 21. The source said one vessel was waiting at Ceyhan to load Kirkuk crude, but no loading was taking place. Storage tanks held 1.9 million barrels of Iraqi crude, the source said.

A bomb attack near Mosul in late October stopped Iraq from pumping crude to Ceyhan until November 2. The pipeline typically pumps 500,000 barrels of oil per day.

Spotlight On Oil

Iraq's oil industry, dilapidated after decades of war, sanctions and underinvestment, suffered frequent bombings and suicide attacks after the 2003 U.S. invasion triggered sectarian warfare and a fierce insurgency. The Ceyhan pipeline was mostly idle until 2007 because of insecurity.

Attacks on oil infrastructure have become less frequent in the last year as overall violence in the country declined.

But the industry has been under a spotlight in the past few weeks after the oil ministry signed the first major new oilfield agreements with global oil majors since the invasion.

The deals have been presented as a major success by the Shi'ite Muslim-led government of Prime Minister Nuri al-Maliki. Sunni Islamist groups like Al-Qaeda are expected to try to undermine Maliki's government ahead of an election next year.

Britain's BP and China's CNPC have clinched a final agreement to operate Iraq's biggest field, Rumaila, and groups led by Italy's Eni and U.S. major Exxon Mobil have secured initial deals over Zubair and West Qurna Phase One.

Japan's Nippon Oil Corp and partners may ink an initial deal in the coming days for Nassiriya.

In December Iraq plans to hold a second round of oilfield tenders, offering up 10 largely undeveloped fields to international oil companies.

The deals have the potential to help Iraq leapfrog to third place in the league of global oil producers, providing it with the billions of dollars it needs to rebuild.